The Development of Ice Cloud Scattering Models

For Use in Remote Sensing Applications

Ice Cloud Research Team:

Bryan A. Baum (UW-Madison)     Ping Yang (Texas A&M)    Andrew J. Heymsfield and Carl Schmitt (NCAR)    

Goals:

  1. Make better use of historical in-situ data collected from cirrus clouds to derive both particle size distributions and particle habit distributions
  2. Develop the most up-to-date set of single scattering properties calculated for a variety of habits, including droxtals, plates, hollow and solid columns, 3D bullet rosettes, and aggregrates.
  3. Develop state-of-the-art ice cloud scattering models for use with various remote sensing instruments, including lidars, satellite imagers, and IR-based interferometers. These scattering models will all be based on the same microphysical models and development methodology.

Note (posted August, 2008): we are in the process of updating our ice models to incorporate several years of improvements, including a new treatment for surface roughening on the ice particles, the addition of hollow bullet rosettes, other improvements in the ice light scattering models, a wealth of new microphysical data from ice clouds (subvisual cirrus, tropical data, recent field campaigns, etc.), and much more. Additionally, models will now be prepared for the entire series of AVHRR imagers as well as for many more geostationary imagers than are available currently on our web site. If you would like to be notified when there are new models, or want me to include a specific imager or sensor, please send me an email.


Ice Cloud Bulk Scattering Models


Based on recent research, these sets of models have been developed and are being explored for application to global cloud retrievals from satellite data. There are a number of issues that we addressed in these models.

  • increased our set of size distributions to account for the range of crystal sizes found in polar, midlatitude, and tropical ice clouds in a more realistic fashion. Currently, we're using over 1100 particle size distributions.
  • increased number of habits to include, for example, 3D bullet rosettes in which we can vary the number of bullets, droxtals, and perhaps more realistic shapes for the very large particles found near the tops of cirrus formed in convective regions
  • increased number of size bins to account for large crystal sizes more realistically account for mixtures of habits found in polar, midlatitude, and tropical ice clouds
  • included mean and standard deviation of microphysical and scattering properties, as determined by averaging between 10-20 individual models about each target effective diameter

Observations of Midlatitude Cirrus

Observations of Tropical Ice Clouds